Optical components used, for example, for a cellular phone or a digital camera have been downsized and sophisticated in recent years. Under a circumstance where miniaturization of those products has been developed dramatically, further miniaturization of the body size and sophistication of the performance are now demanded for the optical components. As a result, further miniaturization and sophistication of an imaging lens unit constituting a camera module or the like is also demanded. In view of such a state, a plastic lens, which is advantageous for miniaturization, has been studied for practicable use for one or more lenses constituting an imaging lens unit, in place of glass lenses.
In the production of electronic components such as parts of a cellular phone, soldering is often performed. Typical conventional soldering processes include the steps of melting solder, and then applying the melted solder on a substrate surface, but now solder reflow processes are replacing such conventional processes. Usually in a solder reflow process, solder is printed in advance on a substrate surface by a technique such as printing, components are mounted on the substrate surface, and then the substrate and components are soldered in a reflow oven. The solder reflow process is advantageous in that it is suitable for soldering fine electronic components, and affords high productivity. Thus, such processes are effective in production of a camera module which is to incorporate a miniaturized imaging lens unit. In the solder reflow process, the reflow oven is heated by hot wind, far infrared rays, or the like heat sources. Thus, the components to be processed by such a process are required to have sufficient thermal resistance against the reflow temperature.
Hence, in order to miniaturize camera modules, a suitable measure must be taken to endure such a solder reflow process, in addition to using a plastic lens. At this time, it is important to miniaturize and sophisticate camera modules without deteriorating the optical characteristics.
As for the conventional technique, Patent Document 1, for example, discloses a lens body which eliminates a restraint member for a lens by providing a clearance between a lens frame and the periphery of the lens to apply an automatic alignment structure to a lens mounting portion, whereby the lens body is prevented from deformation and allows itself to facilitate centering. This technique aims to reduce deformation of the lens resulting from the thermal expansion and mechanical pressure. The structure of the lens body has clearance between the lens frame and the periphery of the lens and, at the lens mounting portion, one or both of the contact face on the annular projection provided in the outer portion of the lens effective diameter and the contact face on the annular projection of the lens frame in contact with the outer portion of the lens effective diameter have a tapered slope or a spherical shape.
In this lens body, the lens installed in the lens frame is, for example, in a state where the annular projection provided in the outer portion of the lens effective diameter is placed on the tapered-slope or spherical annular projection of the lens frame. The lens is not fixed before centering. After the centering, the lens is fixed, with an adhesive, in the lens frame at the annular projection provided in the outer portion of the lens effective diameter.
Further, Patent Document 2, for example, discloses a lens fixing structure that has a lens, and a lens barrel for housing the lens. The lens fixing structure forms a holding portion configured to hold, after housing of the lens in the lens barrel, the lens inside the lens barrel by deforming the internal wall of the barrel.
[Patent Document 1]
    JP 61-121019 A (pages 1 to 3)[Patent Document 2]    JP 2006-195139 A (pages 2 and 5)